Electrolytic refining of metals



Patented Nov. 23, 1926.

UNITED STATES FRANK F. COLCORD, OF NEW YORK, N. Y.,

PATENT OFFICE.

ASSIGNOR TO UNITED STATES SMELTING,

REFINING & MINING COMPANY, OF PORTLAND, MAINE, A CORPORATION OF MAINE.

ELECTROLYTIC REFINING OF METALS.

No Drawing.

The invention relates to the electrodeposition of metals and moreparticularly to the electrodeposition of zinc.

It is the practice in the electrodeposition of zinc to use so-calledaddition reagents in theelectrolyte and the present invention is basedon the discovery of a new reagent of this character which may be usedwith marked advantage oyer prior reagents in the electrodeposition ofzinc. This reagent is a sulphite liquor concentrate comprising the solidor viscous materials obtained from the waste sulphite liquors producedby treating certain woods with sulphite solutions. The

evaporation of these liquors leaves a colloidal substance which ,may bedesignated as sulphite lignose. The principal constituents of thissubstance are or may be lignin sulphuric acid, lignin sulphonic acid,aldehyde sulphonic acids, furfural, and plant sugars.

This substance is cheaply made from the waste sulphite liquors producedfrom the manufacture of paper pulp and is known under the trade nameslignol and goulac.

I have discovered that sulphite lignose may be used as an additionreagent in certain electrolytes with remarkably advantageous results. Itmay be used to replace many of the addition reagents commonly used,weight for weight, and owing to its ex tremely low price, a substantialeconomy may be effected. It may be used alone or in partial replacementof some of the commonly used addition reagents effecting not only aneconomy thereby, but permitting the substitution to take place in an oldelectrolyte and thus avoid the cost of new electrolyte when changingover to this addition reagent. In many cases it produces a cathode depostsuperior to deposits obtained from other addition reagents, increasingthereby the efli- .eiency of the operation and resulting in an importanteconomy in the power consump tion. No accumulation in the electrolyte ofsubstances which might finally cause the deposit to form non-adherentand crystalline Application filed .Tune 1, 1925. Serial No. 34,222.

deposits has been noticed With this addition reagent, as in the casewith some of the prior addition reagents commonly used.

The use of this addition reagent has given particularly excellentresults in the electrodeposition of zinc with a sulphuric acidelectrolyte. lVhile the composition of the electrolyte can varyconsiderably without materially affecting the character of the deposit,excellent results have been obtained with an electrolyte which at thestart contained 100 grams of zinc as zinc sulphate per liter, and whichat the end contained 30 grams of zinc and 100 grams of free sulphuricacid per liter. The common addition reagent in the electrodeposition ofzinc has been glue, but complete substitution of this new additionreagent can be efiected. In actual practice this addition reagent whenused alone is added daily to the electrolyte in the form of a watersolution at the rate of one to two pounds of the dry reagent per ton ofzinc produced, while if used in conjunction with glue the total quantityof the two reagents added daily is one to two pounds per ton of zincproduced with the glue and the new reagent varying in such proportion asdesired. The new reagent alone or in conjunction with other additionreagents produces bright and dense deposits of zinc with sulphuric acidelectrolytes.

What is claimed is:

1. That improvement in the electrodeposition of zinc with sulphuric acidelectrolytes which consists in the use in the acid electrolyte ofsulphite lignose as an addition reagent.

2. That improvement in the electrodeposition of zinc with sulphuric acidelectrolytes which consists in the use as an addition reagent in theacid electrolyte of sul hite lignose. in conjunction with other ad itionreagents.

In testimony whereof I have name to this specification.

FRANK F. COLCORD.

signed my

